1. Field of the Invention
The present invention relates to a nonreciprocal circuit element such as a circulator, an isolator, and so forth that can be used for an antenna multiplexer or the like.
2. Description of the Related Art
The configuration of a typical known nonreciprocal circuit element S2 will be described with reference to FIGS. 7, 8, and 9. The nonreciprocal circuit element S2 includes three central conductors 51. Each of the three central conductors 51 is formed as a metal plate. The three metal plates cross one another and are provided in a hundred-and-twenty degree intervals. The nonreciprocal circuit element S2 further includes a dielectric substrate 52 comprising a dielectric material. The dielectric substrate 52 is molded so that each of the three central conductors 51 is partly imbedded into it. The nonreciprocal circuit element S2 further includes a magnet 53 placed on the three central conductors 51 at the position where they cross one another and a circular ferrite plate 58 placed under the three central conductors 51 at the position where they cross one another. The nonreciprocal circuit element S2 further includes a first yoke 54 formed as a magnetic plate. The first yoke 54 is provided so as to cover the magnet 53, which is placed on the three central conductors 51. The nonreciprocal circuit element S2 further includes a second yoke 55 formed as a magnetic plate with a bottom. The second yoke 55 is provided so as to cover the ferrite plate 58, which is placed under the three central conductors 51. The second yoke 55 is connected to the first yoke 54.
Accordingly, in the nonreciprocal circuit element S2, the first yoke 54 and the second yoke 55 form a magnetic closed circuit. Each of the central conductors 51 has an input/output terminal 51a. The three input/output terminals 51a are protruding from the side of the first yoke 54 and the second yoke 55, which are connected with each other.
A circuit substrate 56 shown in FIG. 8 can be used for an antenna multiplexer or the like. The circuit substrate 56 has a hole 56a, a plurality of conductive patterns 57, and a plurality of chip capacitors C2 that are provided around the hole 56a. 
The configuration of the chip capacitor C2 is shown in FIG. 9. The chip capacitor C2 includes an insulator 61 formed as a ceramic rectangular parallelepiped or the like. The chip capacitor C2 further includes a first electrode 62 and a second electrode 63 that are made of silver or the like. The first and second electrodes 62 and 63 are provided on two flat opposing surfaces of the insulator 61, respectively. A capacitance is formed between the opposing first and second electrodes 62 and 63.
Thus, various electrical parts (not shown) including the plurality of chip capacitors C2 or the like that is to be connected to the nonreciprocal circuit element S2 are provided on the circuit substrate 56, which has the conductive patterns 57 thereon. Subsequently, a desired electronic circuit is formed.
The nonreciprocal circuit element S2 is placed in the hole 56a of the circuit substrate 56. Then, the three input/output terminals 51a each having a ground electrode (not shown) are provided on the conductive patterns 57. The three input/output terminals 51a are soldered to the conductive patterns 57 so that they are connected to one another.
After that, either the first electrode 62 or the second electrode 63 of the chip capacitor C2 is cut out so that the capacitance is adjusted. Subsequently, a desired electrical characteristic is obtained.
Thus, the nonreciprocal circuit element S2 is mounted on the circuit substrate 56, which has the chip capacitors C2 thereon. Therefore, the circuit substrate 56 increases in size. Further, the nonreciprocal circuit element S2 and the chip capacitors C2 have to be separately wired to the circuit substrate 56. Accordingly, the workability of the nonreciprocal circuit element S2 is worsened.